WikiUnits

Convert Density

Density
Dimension ML-3
Common Symbol(s) ρ
SI Unit(s) kg·m-3
Imperial/US Unit(s) lb·ft-3
Other Unit(s) oz·gal-1
Unit conversions
1 kg·m-3 in ... ... is equal to ...
Metric unit(s) 1×10-3 g·cm-3
British/Imperial 0.1335 oz·gal-1
Other unit(s) 6.243×10-2 lb·ft-3

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Metric Conversion
Gram per cubic centimetre [g/cm³]
Kilogram per cubic metre [kg/m³]
Gram per cubic metre [g/m³]
Kilogram per cubic decimetre [kg/dm³]
Imperial/US Conversion
Ounce per gallon (US) [oz/gal]
Pound per cubic foot [lb/ft³]
Pound per cubic inch [lb/in³]
Pound per gallon (US) [lb/gal]

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.

To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material, usually water. Thus a relative density less than one means that the substance floats in water.

The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance (with a few exceptions) decreases its density by increasing its volume. In most materials, heating the bottom of a fluid results in convection of the heat from the bottom to the top, due to the decrease in the density of the heated fluid. This causes it to rise relative to more dense unheated material.

The reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is an intensive property in that increasing the amount of a substance does not increase its density; rather it increases its mass.

This article uses material from the Wikipedia article "Density", which is released under the Creative Commons Attribution-Share-Alike License 3.0.